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Johann (Johan) Schweigger was a chemist, physicist, and professor of mathematics at the Gymnasium of Bayreuth in 1803, at the Polytechnic School of Nuremberg in 1819, and the University of Halle, Germany, sometime in 1820. The first galvanometer was built in Germany by Johann S. Schweigger in 1820. He used Oersted’s discovery of electromagnetism for his invention. Schweigger developed the galvanometer as a tool for measuring the strength and direction of electric current.
Schweigger named this instrument in honour of Luigi Galvani. It is the first sensitive instrument for measuring and detecting small amounts of electricity. Schweigger was born in Erlanger, Bavaria, Germany, on 8 April 1779. He was educated at the University of Erlanger, where he received his PhD degree in 1800. His PhD thesis was on the subject of Homeric Odes. Schweigger’s PhD thesis was carried out under the philosopher Franz August Wolf. Schweigger was, however, later converted to a career in science and mathematics by the chemist/physicist Georg Friedrich Hildebrandt, the mathematician/engineer Karl Christian Langsdorff, and the astronomer Johann Tobias Mayer.
His major academic career was served at the University of Halle between 1820 and 1857. He started the Journal for Chemistry and Physics (Jahrbuch fur Chemie und Physik) in 1811, and continued coediting it until 1828 (54 volumes) when he changed its title to Annales de chemie et de physique. He published several critiques of Volta’s theory of metal contact in animal electricity in the journal.
In 1811 Johann Schweigger proposed name halogen for Chlorine. Chlorine was discovered by Humphrey Davy on July 12, 1810, but it was called Humphrey Davy that time.
Andre-Marie Ampere’s theory of “electrodynamics” was opening many avenues for discoveries when in July 1820 Hans Oersted discovered electromagnetism. William Wollaston of England was the first, however, to advance the possibility of electromagnetic rotations. Schweigger opposed Wollaston’s idea of electromagnetic rotations because he believed that if the idea was true then a magnet should revolve around a wire carrying current. Michael Faraday came along later and demonstrated that the ideas of both Wollaston and Schweigger were true.
Schweigger, however, became one of the first scientists after Oersted’s discovery to demonstrate a determination and an interest in the experimentation of electromagnetism. As coeditor of the Journal for Chemistry and Physics he probably read Oersted’s manuscript submitted to the journal for review and publication. Schweigger then attempted through experimentation, like Oersted, the construction of larger piles to improve the performance of electromagnetism.
He was unsuccessful. During one experiment, however, Schweigger observed that a magnetized needle reversed its direction when connections to the poles of the pile were reversed. He then got the idea that if he made a wire that he was using to pass current into a coil with several turns that it might increase the strength of a magnetic field produced by the current. He used a needle mounted in a vertical plane to detect the current, and then observed that the coil increased the effect on the needle device (an electrometer of 1808).
While experimenting with electromagnetism Schweigger became delighted when the effect was doubled as long as the needle’s position was maintained within the plane of the doubled loop of wire (coil). Next he increased the number of turns or loops on the coil and found that the effect was multiplied. Schweigger wound a conducting wire on itself for 100 turns to provide the effect of being greater than a single loop of wire.
Applying Oersted’s principle to his device he reported the operation and effect of his galvanomagnetic multiplier just two months after Oersted’s announcement in July 1820 of his experiments with electromagnetism. Schweigger presented a paper on his discovery at the University of Halle on 16 September 1820, and published the same in the November 1820 issue of Literary Gazette, Germany. Schweigger called his new device an electromagnetic multiplier (multiplikator) or galvanometer multiplier (or a Galvano-magnetic Kondensator).
The multiplier (multiplicator) was a device to indicate the attraction or repulsion of electricity (detect and measure very small quantities of current), and soon it was accepted as a replacement for the use of the Coulomb’s torsion balance. The multiplier became important for measuring and indicating sources of galvanic current.
Multiplier (multiplicator)
In 1820, Schweigger built a rectangular wooden frame on which he wound an insulated wire. This was called the Schweigger multiplier. A magnetic needle was suspended from a thin thread inside the coil. In the absence of electrical current the needle is oriented according to the magnetic meridian. When an electrical current is passed through the coil on the frame, the needle changes direction; the stronger the current, the more marked the deflection.
His discovery was described to be like Gehlen’s 1808 electroscope which was then used to measure the attraction and repulsion of friction electricity rather than Coulomb’s torsion balance. Schweigger was said to have modified the electroscope of 1808 by coiling an insulated wire several times (turns) around a magnetic needle with the deflecting power of the Voltaic current increasing with the number of turns.
Abbe Francois Moigno (1804-1884) of Paris soon stated (while referring to Schweigger’s discovery) that if a conducting wire was twisted upon itself 100 times a passing current in the wire would then produce an effect 100 times greater than that of a single wire of one turn. Dr Thomas Seebeck of Germany picked up on Moigno’s statement to show that the power of multiplication does not increase with the number of turns as stated because resistance in the unit naturally increases with the length of wire used to decrease power.
Oersted praised Schweigger’s invention by stating that he invented an apparent admirably adapted device for exhibiting by means of the magnetic needle the feeblest electrical currents….. Poggendorff, a distinguished young savant of Berlin constructed an electromagnetic multiplier shortly after Schweigger, and conducted some outstanding experiments with his device.
He had also constructed prototypes of the moving-coil and moving vane galvanometers. The effect of the number of turns in a coil for use in inductance electricity was of considerable value. The invention of Schweigger’s galvanometer may be on the same level to science as the Leyden jar and the pile. He found out that the current was not diminished by increasing the number of coils or turns of wire through which it has passed. The force exerted on the needle turned out to be the number of n times as great with n turns as with only one, because each turn exerts its own forces on the needle independently of the rest.
Johann Poggendorff of Berlin, Germany, independently of Schweigger built a crude galvanometer, also called a multiplier, similarly to that of Schweigger in 1821. Poggendorff has been given credit for inventing the multiturn method of increasing the sensitivity of the detection of electrical current, but historians have favored Schweigger for this invention.
In Cambridge, England, professor James Cumming also used a similar approach to that of both Schweigger and Poggendorff for building a galvanometer. His experiments helped him observe the value of multi turns of wire over that of a single wire in deflecting a magnetic needle. His approach was to reduce the effect of the earth’s magnetic field on the needle. Cumming built his galvanometer with a small magnet underneath the magnetic needle to neutralize the earth’s magnetic field. He than named his device both a galvanoscope and a galvanometer. He presented papers on his invention in April and May 1821, and published his findings in 1822.
The independent work of Schweigger, Poggendorff, and Cumming contributed to the development of the galvanometer. Each reached the conclusion that Oersted’s device could be made more sensitive for detecting electrical currents. Their idea was that more of the wire carrying current needed to face and be ver near the magnetic needle. Also, the flowing current had to remain moving in the same direction. By looping the wire over and around a rectangular piece of metal they increased the area of the wire, and allowed the looped wire to be near the magnetic needle.
He wrote and published Uber das elektron der Alten…… in 1848. He got involved in mythology through his interest in natural history in 1836.
A major problem of Schweigger’s galvanometer was soon discovered. His galvanometer was effected by the magnetic field of the earth often enough to caused faulty measurements. Leopoldo Nobili of Italy fixed the problem sufficiently to make the galvanometer an indispensible measuring tool of electrical current. To prevent the needle always being aligned with the magnetic meridian when there is no current, Nobili, in 1826, devised a static system. This comprised two cylindrical, parallel magnetic bars whose magnetic poles were symmetrically aligned. The system was built in such a way that one of the bars was inside the multiplier and the other outside.
This configuration gave greater sensibility to Nobili’s galvanometer, nullifying the torsion effect of the Earth’s magnetic field. The apparatus with two needles mounted in this way was subjected to two pairs of symmetrical forces, avoiding torsion of the wire when there was no current passing through the multiplier. Schweigger’s multiplier was also improved by Oersted, and Du Bois Reymond which made it a most perfect and delicate means to measure electrical force. In 1858, Lord Kelvin (William Thomson, 1824-1907) added a mirror to the galvanometer to improve the device further.
Johann Schweigger died in Halle, Germany, on 6 September 1857.
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